Electronic faucets of various types and designs are available on the market, however they have not yet succeeded in penetrating the main market. One likely reason for this is that the right combination of proposed advantages over traditional faucets and an affordable price has not yet been found. Also, it is important to note that electronic faucets are potentially hazardous devices, since they can deliver very hot fluid (typically water) that could cause serious burns to a person using it (e.g. while taking a shower). In order to succeed in marketing such products, the customer should be reassured that electronic faucets are safe. Further, the customer wants to be assured that in case of a failure of the system, he or she can still take a shower.
Electronic faucets or mixing devices typically comprise a keypad and a display screen (usually an LCD), generally referred to as electronic I/O (input/output), and a microcomputer that receives data from a temperature sensor (e.g. a thermocouple in the flow stream) and a flow sensor device. The data is compared to the desired temperature and/or flow that has been set (i.e. set point) by the user and a signal is sent to an electronically controlled valve or valves to control the mix of hot and cold water and/or overall flow rate. The electronic I/O can potentially also allow voice activation, proximity activation, etc.
Thus, an electronic faucet can control the dispensing of water at a relatively constant desired temperature and/or flow rate despite potential temperature and pressure deviations that may occur in the water supply while one showers, or for other use. Further, the electronic faucet eliminates the typical trial and error process when attempting to set a desired water temperature and flow rate.
U.S. Pat. No. 4,696,428 (to Shaklis) describes an electronic fluid temperature and flow control system that comprises a mixing valve for controlling the water temperature and a volume control valve for controlling the water flow rate. In light of the issue of providing water even in the event of a failure of the electronic faucet, the system comprises a separate/alternate water pathway with manual valves to allow manual control of the system when needed. When the system is disabled, the manual controls can be used to provide water. The manual controls do not have direct influence on the malfunctioned electronic system which, if not disabled, can still potentially supply undesirably hot or cold water, at least until it is disabled.
U.S. Pat. No. 6,913,203 (to DeLangis) describes a self-powered electronically controlled mixing valve adapted for convenient retrofitting. The mixing valve is powered by a turbine generator, the energy being stored in a battery or capacitor. Water flow rate is controlled by existing hot and cold water valves and the temperature is controlled via a microcomputer of a main control unit by a touch pad. If no response is received from the main control unit, due to a failure such as a turbine or battery failure, the microcomputer will default to a warm water temperature of 85 degrees F. (approx. 30 degrees C.) and produce three long beeps. Should the microcomputer malfunction and allow scalding water to flow, there is failsafe hardware circuitry to disengage a stepper motor from the mixing valve causing the valve to relocate to a 50% hot water and 50% cold water mix. The system additionally comprises a mechanical protection device which limits the maximum possible temperature to 175 degrees F. (approx. 80 degrees C.) should the microcomputer and fail safe circuitry both fail.